JP2006144248A - Hydraulic control device for work vehicle - Google Patents

Hydraulic control device for work vehicle Download PDF

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Publication number
JP2006144248A
JP2006144248A JP2004331888A JP2004331888A JP2006144248A JP 2006144248 A JP2006144248 A JP 2006144248A JP 2004331888 A JP2004331888 A JP 2004331888A JP 2004331888 A JP2004331888 A JP 2004331888A JP 2006144248 A JP2006144248 A JP 2006144248A
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valve
pressure
work vehicle
hydraulic
control device
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JP4685417B2 (en
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Yoshinobu Kobayashi
義伸 小林
Hiroshi Matsuzaki
浩 松崎
Katsumi Ueno
勝美 上野
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Hitachi Construction Machinery Co Ltd
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Hitachi Construction Machinery Co Ltd
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Priority to JP2004331888A priority Critical patent/JP4685417B2/en
Priority to DE102005054394A priority patent/DE102005054394B4/en
Priority to US11/272,741 priority patent/US7703280B2/en
Priority to CN200510114995.5A priority patent/CN1776123B/en
Publication of JP2006144248A publication Critical patent/JP2006144248A/en
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2203—Arrangements for controlling the attitude of actuators, e.g. speed, floating function
    • E02F9/2207—Arrangements for controlling the attitude of actuators, e.g. speed, floating function for reducing or compensating oscillations

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  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Operation Control Of Excavators (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control device for a work vehicle, capable of restraining vibration generated in loading travel, regardless of a weight change in a front part. <P>SOLUTION: This hydraulic control device has a boom cylinder 3 provided in a wheel loader, a operation valve 16 for controlling pressure of a bottom side pressure chamber 3a of this boom cylinder 3, an accumulator 7 connected to the bottom side pressure chamber 3a of the boom cylinder 3 via a connecting pipe 9, an opening-closing valve 5 having a pilot chamber 5a and switching communication and cutoff of the connecting pipe 9 in response to pressure of the pilot chamber 5a, and a switching means for switching supply and discharge of the pressure to the pilot chamber 5a; and is constituted so that this switching means includes a controller 21 for variably controlling opening of the opening-closing valve 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、ホイールローダ等の作業車両に備えられる作業車両用液圧制御装置に関する。   The present invention relates to a hydraulic control device for a work vehicle provided in a work vehicle such as a wheel loader.

ホイールローダの掘削／積み込み作業では、バケットに積み込んだ土砂などを所定の場所まで移動させることが多い。積載走行時、バケットの重量が大きくなっているため、車両の上下運動がブームを上下に揺動させ、その結果車両の振動を増幅させてしまう。   In excavation / loading work of a wheel loader, earth and sand loaded in a bucket are often moved to a predetermined place. Since the weight of the bucket is increased during loading, the vertical movement of the vehicle swings the boom up and down, resulting in amplifying the vibration of the vehicle.

この振動を抑制するために、走行時にはブームシリンダのボトム側圧力室とアキュムレータとを連通し、ボトム側圧力室の圧力変動をアキュムレータに吸収させ、一方、バケット掘削作業時は、アキュムレータとの連通を遮断し、掘削力がアキュムレータに吸収されるのを防ぐ。この種の従来技術として、特許文献１に示されるものがある。   To suppress this vibration, the bottom pressure chamber of the boom cylinder communicates with the accumulator during traveling, and the accumulator absorbs pressure fluctuations in the bottom pressure chamber, while communication with the accumulator is performed during bucket excavation work. Shut off and prevent the drilling force from being absorbed by the accumulator. There exists a thing shown by patent document 1 as this type of prior art.

図９は、特許文献１に示されている図ではないが、この特許文献１に示される技術の要部を示す図である。以下、これを従来技術として説明する。図９に示す従来技術は、作業車両に備えられた液圧シリンダ、すなわちブームシリンダ５１と、このブームシリンダ５１の圧力室の圧力を制御する操作弁、すなわちコントロール弁５４と、このコントロール弁５４とブームシリンダのボトム側圧力室５１ａ、ロッド側圧力室５１ｂとをそれぞれ接続するメイン管路５２、５３が備えられており、メイン管路５２，５３から分岐された分岐回路５０を有する。分岐回路５０は、メイン管路５２、５３から分岐された分岐管路５５，５６を有し、それぞれ開閉弁５７を介してアキュムレータ５８およびタンク６１に接続されている。開閉弁５７はコントローラ６０からの信号を受けて電磁弁５９が切り替わることで閉位置Ｇ、開位置Ｈに切り換えられる。   FIG. 9 is not a diagram shown in Patent Document 1, but is a diagram showing a main part of the technique disclosed in Patent Document 1. Hereinafter, this will be described as a conventional technique. The prior art shown in FIG. 9 includes a hydraulic cylinder provided in a work vehicle, that is, a boom cylinder 51, an operation valve that controls the pressure in the pressure chamber of the boom cylinder 51, that is, a control valve 54, and the control valve 54. Main pipelines 52 and 53 are provided for connecting the bottom pressure chamber 51a and the rod pressure chamber 51b of the boom cylinder, respectively, and a branch circuit 50 branched from the main pipelines 52 and 53 is provided. The branch circuit 50 has branch pipelines 55 and 56 branched from main pipelines 52 and 53, and is connected to an accumulator 58 and a tank 61 via on-off valves 57, respectively. The on-off valve 57 is switched between the closed position G and the open position H when the electromagnetic valve 59 is switched in response to a signal from the controller 60.

バケット掘削作業時は、開閉弁５７は閉位置Ｇの状態であり、ブームシリンダ５１のボトム側圧力室５１ａとアキュムレータ５８との連通は遮断されており、ブームシリンダ５１に作用する掘削力がアキュムレータ５８に吸収されるのを防いでいる。   During the bucket excavation work, the on-off valve 57 is in the closed position G, the communication between the bottom pressure chamber 51a of the boom cylinder 51 and the accumulator 58 is cut off, and the excavating force acting on the boom cylinder 51 is accumulated in the accumulator 58. To prevent absorption.

走行時は電磁弁５９を切り換え、開閉弁５７を開位置Ｈに切り換え、ブームシリンダ５１のボトム側圧力室５１ａとアキュムレータ５８を連通させ、ボトム側圧力室５１ａの負荷変動をアキュムレータ５８に吸収させることで車両の振動が抑制される。
特開２０００−３０９９５３公報 When traveling, the solenoid valve 59 is switched, the on-off valve 57 is switched to the open position H, the bottom pressure chamber 51a of the boom cylinder 51 and the accumulator 58 are connected, and the load fluctuation of the bottom pressure chamber 51a is absorbed by the accumulator 58. This suppresses the vibration of the vehicle.
JP 2000-309953 A

上述した従来技術では、ブームシリンダ５１のボトム側圧力室５１ａとアキュムレータ５８との連通／遮断を切り換える開閉弁５７が設けられているが、連通時は前記開閉弁５７の開度は常に一定となっていた。しかしながら、バケットに積み込まれる積載物や車格、フロントアタッチメント等によってフロント部の重量が変化する。フロント部の重量に対して開閉弁５７の開度が小さすぎると、ブームにかかる負荷をアキュムレータ５７に吸収しきれなくなる場合がある。すなわち、振動を抑制できなくなる場合がある。逆に、フロント部の重量に対して開度が大きすぎると、フロント部の振動が減衰しきれずに作業車両の車体が揺れて不安定になる場合がある。つまり、従来技術ではフロント部の重量変化に伴って振動を十分に吸収できない場合がある。   In the above-described prior art, the opening / closing valve 57 for switching communication / blocking between the bottom pressure chamber 51a of the boom cylinder 51 and the accumulator 58 is provided, but the opening degree of the opening / closing valve 57 is always constant during communication. It was. However, the weight of the front portion varies depending on the load, vehicle case, front attachment, and the like loaded in the bucket. If the opening of the on-off valve 57 is too small relative to the weight of the front portion, the load applied to the boom may not be absorbed by the accumulator 57 in some cases. In other words, vibration may not be suppressed. Conversely, if the opening is too large with respect to the weight of the front part, the vibration of the front part may not be attenuated and the vehicle body of the work vehicle may shake and become unstable. That is, in the conventional technique, there is a case where the vibration cannot be sufficiently absorbed with the change in the weight of the front portion.

本発明の目的は、フロント部の重量変化にかかわらず、積載走行時に生じる振動を抑えることができる作業車両用液圧制御装置を提供することである。   An object of the present invention is to provide a hydraulic pressure control device for a work vehicle that can suppress vibrations that occur during loading and traveling regardless of a change in weight of a front portion.

上記目的を達成するために、本発明は、作業車両に備えられ、液圧シリンダと、この液圧シリンダの圧力室の圧力を制御する操作弁と、前記液圧シリンダの圧力室に接続管路を介して接続されたアキュムレータと、パイロット室を有し、且つ前記パイロット室の圧力に応じて前記接続管路の連通および遮断を切り換える開閉弁と、前記パイロット室への圧力の供給および排出を切り換える切換手段とを有する作業車両用液圧制御装置において、前記切換手段は、前記開閉弁の開度を可変に制御する制御手段を含むことを特徴としている。   In order to achieve the above object, the present invention is provided in a work vehicle, and includes a hydraulic cylinder, an operation valve for controlling the pressure of the pressure chamber of the hydraulic cylinder, and a connecting line to the pressure chamber of the hydraulic cylinder An accumulator connected via a valve, a pilot chamber, and an on-off valve that switches between connection and disconnection of the connection line according to the pressure in the pilot chamber, and switching between supply and discharge of pressure to the pilot chamber In the hydraulic control apparatus for a work vehicle having switching means, the switching means includes control means for variably controlling the opening degree of the on-off valve.

このように構成した本発明によれば、フロント部の重量が比較的小さい場合には、開閉弁の開度が小さくなるように制御手段によって制御すればよく、逆にフロント部の重量が大きい場合には、開閉弁の開度が大きくなるように制御手段によって制御すればよい。すなわち、フロント部の重量変化に応じて制御手段によって開閉弁の開度を最適な開度に制御できるので、フロント部の重量変化にかかわらず、積載走行時に生じる振動を抑えることができる。   According to the present invention configured as described above, when the weight of the front portion is relatively small, it may be controlled by the control means so that the opening degree of the on-off valve becomes small. Conversely, when the weight of the front portion is large In this case, the control means may control the opening degree of the on-off valve to be large. That is, since the opening degree of the on-off valve can be controlled to the optimum opening degree by the control means in accordance with the change in the weight of the front part, it is possible to suppress vibrations that occur during loading travel regardless of the change in the weight of the front part.

また本発明は、前記の発明において、前記切換手段が、前記開閉弁を制御する電磁比例弁を含むことを特徴としている。   According to the present invention, in the above invention, the switching means includes an electromagnetic proportional valve that controls the on-off valve.

また本発明は、前記の発明において、前記液圧シリンダの負荷圧力を検知し、その負荷圧力に応じた信号を出力する負荷圧力検知手段を備え、前記制御手段は、この負荷圧力検知手段から出力される信号に応じて前記開閉弁の開度を可変させることを特徴としている。   The present invention further comprises load pressure detecting means for detecting a load pressure of the hydraulic cylinder and outputting a signal corresponding to the load pressure, and the control means outputs the load pressure from the load pressure detecting means. The opening degree of the on-off valve is varied according to the signal to be transmitted.

また本発明は、前記の発明において、前記作業車両の車速を検知し、その車速に応じた信号を出力する車速検知手段を備え、前記制御手段は、この車速検知手段から出力される信号に応じて前記開閉弁の開度を可変にさせることを特徴としている。   According to the present invention, there is provided vehicle speed detection means for detecting a vehicle speed of the work vehicle and outputting a signal corresponding to the vehicle speed, and the control means is responsive to a signal output from the vehicle speed detection means. Thus, the opening degree of the on-off valve is made variable.

また本発明は、前記の発明において、オペレータの入力に応答して前記開閉弁の開度を指示する信号を出力する開度指示手段を備え、前記制御手段は、この開度指示手段から出力される信号に応じて前記開閉弁の開度を可変にさせることを特徴としている。   The present invention further comprises an opening degree instruction means for outputting a signal for instructing an opening degree of the on-off valve in response to an input from an operator, and the control means is output from the opening degree instruction means. It is characterized in that the opening degree of the on-off valve is made variable according to the signal.

また本発明は、前記の発明において、前記接続管路から分岐し、前記開閉弁に並列に配置されるバイパス管路上に設けられ、通常は前記バイパス管路を連通させ、前記液圧シリンダの負荷圧力が所定圧力以上になったときに前記バイパス管路を遮断する切換弁を備えたことを特徴としている。   Further, the present invention is the above invention, wherein the present invention is provided on a bypass line that branches from the connection line and is arranged in parallel with the on-off valve, and usually connects the bypass line to load the hydraulic cylinder. A switching valve is provided that shuts off the bypass pipe when the pressure exceeds a predetermined pressure.

また本発明は、前記の発明において、前記バイパス管路に、前記液圧シリンダから前記アキュムレータへの圧力のみを伝えるチェック弁を設けたことを特徴としている。   According to the present invention, in the above invention, a check valve that transmits only pressure from the hydraulic cylinder to the accumulator is provided in the bypass pipe.

本発明は、制御手段によってフロント部の重量に応じて開閉弁の開度を可変に制御することができるため、フロント部の重量変化にかかわらず、積載走行時に生じる振動を抑えることができ、従来に比べて振動抑制性能を向上させることができる。   In the present invention, the opening of the on-off valve can be variably controlled by the control means according to the weight of the front part, so that vibrations that occur during loading can be suppressed regardless of the weight change of the front part. Compared to the above, vibration suppression performance can be improved.

以下、本発明に関わる作業車両用液圧制御装置を実施するための最良の形態を図に基づいて説明する。   The best mode for carrying out the working vehicle hydraulic control apparatus according to the present invention will be described below with reference to the drawings.

図１は本発明に係る作業車両用液圧制御装置の第１実施形態が適用される作業車両の一例として挙げたホイールローダを示す外観図である。ホイールローダは車体に取り付けられるブーム１と、ブーム１の先端に取り付けられるバケット２を有し、これらのブーム１およびバケット２のそれぞれは一対のブームシリンダ３およびバケットシリンダ４により駆動可能となっている。   FIG. 1 is an external view showing a wheel loader cited as an example of a work vehicle to which a first embodiment of a hydraulic control device for a work vehicle according to the present invention is applied. The wheel loader has a boom 1 attached to the vehicle body and a bucket 2 attached to the tip of the boom 1, and each of the boom 1 and the bucket 2 can be driven by a pair of boom cylinders 3 and bucket cylinders 4. .

［第１実施形態］
図２は本発明に係る作業車両用液圧制御装置の第１実施形態を示す回路図である。この第１実施形態に係る油圧制御装置は、ブームシリンダ３の駆動用のメイン回路から分岐した分岐回路２４を有する。ブームシリンダ３のボトム側圧力室３ａおよびロッド側圧力室３ｂはそれぞれメイン管路１４および１５を介して操作弁１６に接続されている。操作弁１６は、操作レバー１７の操作量に応じて油圧ポンプＰからの圧力をブームシリンダ３のボトム側圧力室３ａまたはロッド側圧力室３ｂへ伝え、他方の圧力室とタンクＴを連通させる。これによりブームシリンダ３は伸縮運動を行う。 [First Embodiment]
FIG. 2 is a circuit diagram showing a first embodiment of a hydraulic control apparatus for a work vehicle according to the present invention. The hydraulic control apparatus according to the first embodiment has a branch circuit 24 branched from a main circuit for driving the boom cylinder 3. The bottom side pressure chamber 3a and the rod side pressure chamber 3b of the boom cylinder 3 are connected to the operation valve 16 via main pipe lines 14 and 15, respectively. The operation valve 16 transmits the pressure from the hydraulic pump P to the bottom-side pressure chamber 3a or the rod-side pressure chamber 3b of the boom cylinder 3 in accordance with the operation amount of the operation lever 17, and makes the other pressure chamber communicate with the tank T. Thereby, the boom cylinder 3 performs a telescopic motion.

分岐回路２４は、メイン管路１４および１５から分岐された分岐管路９および１０を備え、開閉弁５を介してそれぞれアキュムレータ７およびタンクＴに接続可能になっている。ここで、分岐管路９はブームシリンダ３のボトム側圧力室３ａとアキュムレータ７を、分岐管路１０はブームシリンダ３のロッド側圧力室３ｂとタンクＴをそれぞれ接続する。   The branch circuit 24 includes branch lines 9 and 10 branched from the main lines 14 and 15, and can be connected to the accumulator 7 and the tank T via the on-off valve 5. Here, the branch line 9 connects the bottom side pressure chamber 3a of the boom cylinder 3 and the accumulator 7, and the branch line 10 connects the rod side pressure chamber 3b of the boom cylinder 3 and the tank T, respectively.

開閉弁５は、４ポート２位置の切換弁で、圧力源８の圧力が電磁比例弁１２、パイロット管路１３を介して圧力室５ａに伝えられることで駆動される。開閉弁５の他方の圧力室５ｂはドレン管路１１、分岐管路１０を介してタンクＴに接続している。また、圧力室５ｂには復帰ばね６が備えられている。   The on-off valve 5 is a 4-port 2-position switching valve, and is driven by the pressure of the pressure source 8 being transmitted to the pressure chamber 5 a via the electromagnetic proportional valve 12 and the pilot pipe line 13. The other pressure chamber 5 b of the on-off valve 5 is connected to the tank T via the drain line 11 and the branch line 10. The pressure chamber 5b is provided with a return spring 6.

開閉弁５は通常復帰ばね６に押されて閉位置Ａの状態であり、分岐管路９、１０は遮断されている。圧力室５ａに圧力が伝えられると開位置Ｂへと移行し分岐管路９、１０はそれぞれアキュムレータ７、タンクTへ接続される。   The on-off valve 5 is normally pushed by the return spring 6 and is in the closed position A, and the branch pipes 9 and 10 are shut off. When the pressure is transmitted to the pressure chamber 5a, it moves to the open position B and the branch pipes 9, 10 are connected to the accumulator 7 and the tank T, respectively.

電磁比例弁１２は、開閉弁５の開度を可変に制御する制御手段、例えばコントローラ２１から電気信号を受けて開閉する。電磁比例弁１２が中立保持されている場合は位置Ｃの状態であり、圧力室５ａを、パイロット管路１３を介してタンクＴに接続している。コントローラ２１から信号を受けると信号に応じて電磁比例弁１２は位置Ｄへ移行し、圧力源８の圧力を、パイロット管路１３を介して圧力室５ａへ伝える。コントローラ２１にはブームシリンダ３のボトム側圧力室３ａに接続され、このボトム側圧力室３ａの負荷圧力を検知し、その負荷圧力に応じた信号を出力する負荷圧力検知手段、例えば圧力センサ１８、このホイールローダの走行速度を検知し、車速に応じた信号を出力する車速検知手段、例えば速度センサ１９、オペレータの入力に応答して開閉弁５の開度を指示する信号を出力する開度指示手段、例えば指示スイッチ２０が電気的に接続されており、各信号に相当した制御信号を電磁比例弁１２に出力する。   The electromagnetic proportional valve 12 opens and closes in response to an electrical signal from a control unit that variably controls the opening degree of the on-off valve 5, for example, the controller 21. When the electromagnetic proportional valve 12 is neutrally held, it is in the position C, and the pressure chamber 5 a is connected to the tank T via the pilot line 13. In response to the signal from the controller 21, the electromagnetic proportional valve 12 moves to the position D according to the signal, and transmits the pressure of the pressure source 8 to the pressure chamber 5a via the pilot line 13. The controller 21 is connected to the bottom pressure chamber 3a of the boom cylinder 3, detects the load pressure of the bottom pressure chamber 3a, and outputs a signal corresponding to the load pressure, for example, a pressure sensor 18, Vehicle speed detecting means for detecting the traveling speed of the wheel loader and outputting a signal corresponding to the vehicle speed, for example, a speed sensor 19, an opening degree instruction for outputting a signal for instructing the opening degree of the on-off valve 5 in response to an operator input. Means, for example, an instruction switch 20 is electrically connected, and a control signal corresponding to each signal is output to the electromagnetic proportional valve 12.

なお、上述したコントローラ２１と、電磁比例弁１２と、圧力源８によって、開閉弁５のパイロット室５ａへの供給および排出を切り換える切換手段が構成されている。   Note that the controller 21, the electromagnetic proportional valve 12, and the pressure source 8 described above constitute switching means for switching between supply and discharge of the on-off valve 5 to the pilot chamber 5a.

また、分岐回路２４には、コック２２およびリリーフ弁２３が設けられており、アキュムレータ７とタンクＴとの間に、それぞれ並列に配置されている。   Further, the branch circuit 24 is provided with a cock 22 and a relief valve 23, which are arranged in parallel between the accumulator 7 and the tank T, respectively.

図３は、図２中に示した開閉弁５の開口特性の一例を示している。横軸は電磁比例弁１２がコントローラ２１から受ける制御電流、縦軸は開閉弁５の開度を示している。電磁比例弁１２に制御電流が伝わると、電流値に応じて圧力室５ａに圧力が伝わり開閉弁５がストロークする。開閉弁５の開度の最大値は、ブームシリンダ３の負荷圧力の想定し得る最大値にあわせている。また、開度が最大、即ち開閉弁５がフルストロークしたときの電流値をｉmaxとしている。図３の例では、開閉弁５にはノッチ、すなわち切欠が形成されており、開度を微小に制御可能な範囲を設けている。   FIG. 3 shows an example of the opening characteristic of the on-off valve 5 shown in FIG. The horizontal axis indicates the control current received by the electromagnetic proportional valve 12 from the controller 21, and the vertical axis indicates the opening degree of the on-off valve 5. When the control current is transmitted to the electromagnetic proportional valve 12, the pressure is transmitted to the pressure chamber 5a according to the current value, and the on-off valve 5 is stroked. The maximum value of the opening degree of the on-off valve 5 is adjusted to the maximum value that can be assumed for the load pressure of the boom cylinder 3. Further, the current value when the opening degree is maximum, that is, when the on-off valve 5 has made a full stroke, is imax. In the example of FIG. 3, the on-off valve 5 is formed with a notch, that is, a notch, and provides a range in which the opening degree can be controlled minutely.

図４は、図２中に示したブームシリンダ３のボトム側圧力室３ａの負荷圧力とコントローラ２１で設定される係数関数の関係の一例である。横軸はブームシリンダ３のボトム側圧力室３ａの負荷圧力、縦軸はコントローラ２１内の出力演算用の係数ｅｐを示している。この例では、圧力センサ１8で検出した圧力から、電磁比例弁１２へ出力する制御電流の大きさを決定する係数ｅｐ（０から１の範囲）を演算する。負荷圧力が大きくなるほど係数ｅｐも大きくなり制御電流も大きくなる。   FIG. 4 is an example of the relationship between the load pressure in the bottom pressure chamber 3a of the boom cylinder 3 shown in FIG. The horizontal axis represents the load pressure of the bottom pressure chamber 3a of the boom cylinder 3, and the vertical axis represents the output calculation coefficient ep in the controller 21. In this example, a coefficient ep (range from 0 to 1) for determining the magnitude of the control current output to the electromagnetic proportional valve 12 is calculated from the pressure detected by the pressure sensor 18. As the load pressure increases, the coefficient ep increases and the control current also increases.

図５は、車速と図２中に示したコントローラ２１で設定される係数関数の関係の一例である。横軸は車両の車速、縦軸はコントローラ２１内の出力演算用の係数ｅｖを示している。この例では、速度センサ１９で検出した走行速度から、電磁比例弁１２へ伝える制御電流の大きさを決定する係数ｅｖ（０から１の範囲）を演算する。車速が所定の値Ｖ０になると、開閉弁５が接続状態になるような値ＳＰになり、開閉弁５が開き始める。車速が大きくなるほど係数ｅｖは大きくなり制御電流も大きくなる。なお、図４、図５で示した係数ｅｐ、ｅｖについては後に説明する。   FIG. 5 shows an example of the relationship between the vehicle speed and the coefficient function set by the controller 21 shown in FIG. The horizontal axis represents the vehicle speed, and the vertical axis represents the output calculation coefficient ev in the controller 21. In this example, a coefficient ev (range from 0 to 1) for determining the magnitude of the control current transmitted to the electromagnetic proportional valve 12 is calculated from the traveling speed detected by the speed sensor 19. When the vehicle speed reaches a predetermined value V0, the value SP becomes such that the on-off valve 5 is in a connected state, and the on-off valve 5 starts to open. As the vehicle speed increases, the coefficient ev increases and the control current also increases. The coefficients ep and ev shown in FIGS. 4 and 5 will be described later.

図６は、図２中に示した指示スイッチ２０の操作量とコントローラ２１で設定される制御電流の関係の一例である。横軸は指示スイッチ２０の操作量すなわちオペレータの指示量、縦軸は電磁比例弁１２への制御電流を示している。この例では、負荷圧力や走行速度に関わらず、オペレータの指示量によって電磁比例弁１２への制御電流の大きさが決定され、指示量が大きいほど開閉弁５の開度が大きくなる。   FIG. 6 is an example of the relationship between the operation amount of the instruction switch 20 shown in FIG. 2 and the control current set by the controller 21. The horizontal axis represents the operation amount of the instruction switch 20, that is, the operator instruction amount, and the vertical axis represents the control current to the electromagnetic proportional valve 12. In this example, the magnitude of the control current to the electromagnetic proportional valve 12 is determined by the instruction amount of the operator regardless of the load pressure and the traveling speed, and the opening degree of the on-off valve 5 increases as the instruction amount increases.

図７は、図２中に示したコントローラ２１が実行する処理の一例を示すフローチャートである。このホイールローダが作業を行っているとき、コントローラ２１は圧力センサ１８、速度センサ１９、指示スイッチ２０からの信号を受ける（Ｓ１、Ｓ２、Ｓ３）。このとき、指示スイッチ２０からの信号があるかを判定し（Ｓ４）、信号があれば指示量に応じた制御電流を出力する（Ｓ５）。信号がなければ負荷圧力や走行速度に応じた制御電流を演算して（Ｓ６）電磁比例弁１２に出力する。   FIG. 7 is a flowchart showing an example of processing executed by the controller 21 shown in FIG. When the wheel loader is working, the controller 21 receives signals from the pressure sensor 18, the speed sensor 19, and the instruction switch 20 (S1, S2, S3). At this time, it is determined whether there is a signal from the instruction switch 20 (S4), and if there is a signal, a control current corresponding to the instruction amount is output (S5). If there is no signal, a control current corresponding to the load pressure and traveling speed is calculated (S6) and output to the electromagnetic proportional valve 12.

ここで、制御電流の演算について説明する。図４および図５では、コントローラ２１で負荷圧力や走行速度に応じた係数ｅｐやｅｖを演算した。ここで、これらの係数ｅｐ、ｅｖと、図３で示した開閉弁５がフルストロークするための制御電流ｉmaxの積を電磁比例弁１２の制御電流としている。その結果、ブームシリンダ３の負荷が大きくなるほど、走行速度が大きくなるほど制御電流は大きくなり、開閉弁５の開度も大きくなる。また、負荷圧力が大きくても、図５に示すように走行速度がある大きさにならないときは、掘削走行とみなし、制御電流は小さく開閉弁５は開かない。   Here, the calculation of the control current will be described. 4 and 5, the controller 21 calculates the coefficients ep and ev according to the load pressure and the traveling speed. Here, the product of these coefficients ep and ev and the control current imax for full stroke of the on-off valve 5 shown in FIG. As a result, as the load on the boom cylinder 3 increases, the control current increases as the traveling speed increases, and the opening degree of the on-off valve 5 also increases. Further, even if the load pressure is large, if the traveling speed does not reach a certain level as shown in FIG. 5, it is regarded as excavation traveling, the control current is small, and the on-off valve 5 is not opened.

図２から図７を参照にして第１実施形態の油圧制御装置の動作を説明する。ここで、図１に示すホイールローダの動作をあわせて説明するため、指示スイッチ２０の信号がない場合の動作とする。   The operation of the hydraulic control apparatus according to the first embodiment will be described with reference to FIGS. Here, in order to explain the operation of the wheel loader shown in FIG. 1, the operation is performed when there is no signal from the instruction switch 20.

図１のホイールローダが掘削や積込作業や掘削走行を行っている場合、図７で説明したように、走行速度が小さいため、電磁比例弁１２への制御電流値は小さく、開閉弁５の圧力室５ａにはばね６のセット荷重に抗うのに十分な圧力が供給されない。よって、開閉弁５は閉位置Ａの状態、即ち、分岐管路９および１０は遮断された状態にある。   When the wheel loader of FIG. 1 is performing excavation, loading work, or excavation traveling, as described in FIG. 7, since the traveling speed is small, the control current value to the electromagnetic proportional valve 12 is small, and the on-off valve 5 A pressure sufficient to resist the set load of the spring 6 is not supplied to the pressure chamber 5a. Therefore, the on-off valve 5 is in the closed position A, that is, the branch pipes 9 and 10 are shut off.

ホイールローダが積載走行を行う場合、前述したように負荷圧力や車速に応じた制御電流がコントローラ２１により電磁比例弁１２へ出力され、出力値に応じて圧力源８からの圧力を制御して開閉弁５の圧力室５ａへ伝える。圧力室５ａに加えられた圧力がばね６のセット荷重に抗うのに十分な大きさになると、圧力室５ａの圧力に応じて開閉弁５はストロークし、開位置Ｂ側の状態、すなわち分岐管路９および１０は接続状態になり、走行中ではブーム１の揺れがブームシリンダ３から分岐管路９を介してアキュムレータ７に吸収される。ここで、ホイールローダのフロント部の荷重、すなわちブームシリンダ３の負荷圧力が大きい場合には、開閉弁５の開度が大きくなり、フロント部の荷重が小さい場合には開閉弁５の開度は小さくなる。   When the wheel loader performs loading traveling, as described above, the control current according to the load pressure and the vehicle speed is output to the electromagnetic proportional valve 12 by the controller 21, and the pressure from the pressure source 8 is controlled according to the output value to open and close. This is transmitted to the pressure chamber 5a of the valve 5. When the pressure applied to the pressure chamber 5a becomes large enough to withstand the set load of the spring 6, the on-off valve 5 strokes according to the pressure in the pressure chamber 5a, that is, the state on the open position B side, that is, the branch pipe The roads 9 and 10 are connected, and the boom 1 is absorbed by the accumulator 7 from the boom cylinder 3 through the branch pipe 9 during traveling. Here, when the load of the front part of the wheel loader, that is, the load pressure of the boom cylinder 3 is large, the opening degree of the on-off valve 5 is large, and when the load on the front part is small, the opening degree of the on-off valve 5 is Get smaller.

このように構成した第１実施形態によれば、開閉弁５の開度をコントローラ２１によって負荷圧力や車速に応じて可変に制御することから、フロント部の重量、例えば積荷の有無や車格、フロントアタッチメントの変化などによるブームシリンダ３の負荷や、車速に応じた適切な開度に制御でき、走行中のホイールローダの振動を良好に抑制できる。すなわち、優れた振動抑制性能を確保することができる。   According to the first embodiment configured as described above, the opening degree of the on-off valve 5 is variably controlled by the controller 21 in accordance with the load pressure and the vehicle speed. It is possible to control the opening of the boom cylinder 3 due to a change in the front attachment or the like and an appropriate opening degree according to the vehicle speed, and to satisfactorily suppress the vibration of the wheel loader during traveling. That is, excellent vibration suppression performance can be ensured.

［第２実施形態］
前述した第１実施形態は、開閉弁５が閉位置Ａの状態にあるとき、アキュムレータ７の圧力は、直前の開位置Ｂの状態であったときのブームシリンダ３のボトム側圧力室３ａとほぼ等しくなっている。しかしながら、ブームシリンダ３の負荷圧力は、積荷の重量やブーム１の保持角度等により常に変化する。そのため、開閉弁５が再び開位置Ｂに切り換えられた瞬間に、ブームシリンダ３のボトム側圧力室３ａとアキュムレータ７との間に圧力差が生じていることが多く、この圧力差によってブーム１の急な落ち込み等の不所望な動作や、それによるショックが発生し乗り心地に悪影響を与える場合がある。 [Second Embodiment]
In the first embodiment described above, when the on-off valve 5 is in the closed position A, the pressure of the accumulator 7 is substantially the same as that of the bottom pressure chamber 3a of the boom cylinder 3 in the previous open position B. Are equal. However, the load pressure of the boom cylinder 3 always changes depending on the weight of the load, the holding angle of the boom 1 and the like. Therefore, at the moment when the on-off valve 5 is switched to the open position B again, there is often a pressure difference between the bottom pressure chamber 3a of the boom cylinder 3 and the accumulator 7, and this pressure difference causes the boom 1 to Undesirable movements such as a sudden drop or a shock caused thereby may adversely affect the ride comfort.

図８は本発明に係る作業車両用液圧制御装置の第２実施形態を示す回路図である。第２実施形態の説明に際し、第１実施形態と同等の箇所には同一の符号にて示し、説明も省略する。第１実施形態と異なる箇所のみを説明する。   FIG. 8 is a circuit diagram showing a second embodiment of the hydraulic control apparatus for a work vehicle according to the present invention. In the description of the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is also omitted. Only portions different from the first embodiment will be described.

ブームシリンダ３のボトム側圧力室３ａとアキュムレータ７を接続する分岐管路９に、バイパス管路２６を開閉弁５に対し並列に配置し、バイパス管路２６上に、上流から絞り２５、切換弁２７が配置されている。切換弁２７は２ポート２位置の切換弁で、切換弁２７の一方の圧力室２７ａには、絞り２５の下流側の圧力が導かれ、他方の圧力室２７ｂには、ドレン管路３１を介してタンクＴに接続され、また、復帰ばね２８が備えられている。   A bypass line 26 is arranged in parallel with the on-off valve 5 in the branch line 9 that connects the bottom pressure chamber 3a of the boom cylinder 3 and the accumulator 7, and a throttle 25 and a switching valve are provided on the bypass line 26 from upstream. 27 is arranged. The switching valve 27 is a 2-port 2-position switching valve. The pressure on the downstream side of the throttle 25 is guided to one pressure chamber 27 a of the switching valve 27, and a drain line 31 is connected to the other pressure chamber 27 b. And a return spring 28 is provided.

切換弁２７は、通常は開位置Ｅの状態であり、ブームシリンダ３のボトム側圧力室３ａとアキュムレータ７はバイパス管路２６を介して接続状態となる。ここで、ブームシリンダ３のボトム側圧力室３ａの圧力が上昇し、圧力室２７ａの圧力が復帰ばね２８で設定された圧力よりも大きくなると、切換弁２７は閉位置Ｆに切り換わり、バイパス管路２６を遮断状態になる。   The switching valve 27 is normally in the open position E, and the bottom pressure chamber 3 a of the boom cylinder 3 and the accumulator 7 are connected via the bypass line 26. Here, when the pressure in the bottom pressure chamber 3a of the boom cylinder 3 rises and the pressure in the pressure chamber 27a becomes larger than the pressure set by the return spring 28, the switching valve 27 is switched to the closed position F, and the bypass pipe The path 26 is cut off.

また、切換弁２７の開位置Ｅにはチェック弁２９が設けられており、ブームシリンダ３のボトム側圧力室３ａからアキュムレータ７への流れのみを許容している。   Further, a check valve 29 is provided at the open position E of the switching valve 27, and only the flow from the bottom side pressure chamber 3 a of the boom cylinder 3 to the accumulator 7 is allowed.

このように構成した第２実施形態によれば、開閉弁５が閉位置Ａの状態であっても、ブームシリンダ３のボトム側圧力室３ａとアキュムレータ７はバイパス管路２６を介して接続していることから、アキュムレータ７の圧力はブームシリンダ３のボトム側圧力室３ａに近づき、双方の圧力差は小さくなり、開閉弁５が開位置Ｂに切り換えられた瞬間でもブーム１の不所望な動作は緩和でき、車両へのショックも抑えられる。また、バイパス管路２６には絞り２５が設けられているため、ブームシリンダ３に作用する掘削力がアキュムレータに吸収されるのを抑制している。その他の作用、効果については第１実施形態と同様である。   According to the second embodiment configured in this way, even when the on-off valve 5 is in the closed position A, the bottom pressure chamber 3a of the boom cylinder 3 and the accumulator 7 are connected via the bypass line 26. Therefore, the pressure of the accumulator 7 approaches the bottom side pressure chamber 3a of the boom cylinder 3, the pressure difference between the two becomes small, and even when the on-off valve 5 is switched to the open position B, an undesired operation of the boom 1 is performed. It can alleviate and reduce the shock to the vehicle. Further, since the throttle 25 is provided in the bypass pipeline 26, the excavation force acting on the boom cylinder 3 is suppressed from being absorbed by the accumulator. Other operations and effects are the same as in the first embodiment.

なお、上述の第１、第２実施形態において、コントローラ２１に、負荷圧力や車速と係数関数ｅｐ、ｅｖの関係を設定しているが、本発明はこれに限らず、負荷圧力や車速と制御電流との関係を設定してもよい。   In the first and second embodiments described above, the controller 21 sets the relationship between the load pressure and vehicle speed and the coefficient functions ep and ev. However, the present invention is not limited to this, and the load pressure and vehicle speed and control are controlled. You may set the relationship with an electric current.

また、上述の第１、第２実施形態において、コントローラ２１に計時手段を設け、速度センサ１９からの信号をコントローラ２１が入力した時点から計時手段が時間を計測し、例えば所定時間の間は、開閉弁５の開度を比較的小さく保つ制御信号、すなわち制御電流をコントローラ２１から電磁比例弁１２に出力させるようにし、上述の所定時間を超えた時点からは開閉弁５の開度を徐々に大きく変化させる制御電流をコントローラ２１から電磁比例弁１２に出力させるように構成してもよい。   Further, in the first and second embodiments described above, the controller 21 is provided with time measuring means, and the time measuring means measures the time from when the controller 21 inputs a signal from the speed sensor 19, for example, for a predetermined time, A control signal for keeping the opening of the on-off valve 5 relatively small, that is, a control current is output from the controller 21 to the electromagnetic proportional valve 12, and the opening of the on-off valve 5 is gradually increased from the time when the predetermined time is exceeded. You may comprise so that the control current changed greatly may be output from the controller 21 to the electromagnetic proportional valve 12.

このように構成したものでは、積載走行が始まった際に、開閉弁５の開度を閉状態Ａから開状態Ｂに、さらに開度が小さい状態から開度が大きくなる状態へと滑らかに移行させることができる。これにより、開閉弁５の開動作に伴ってホイールローダに与える衝撃の発生を防ぐことができる。   With such a configuration, when loading and running starts, the opening degree of the on-off valve 5 smoothly transitions from the closed state A to the open state B, and further from a smaller opening degree to a larger opening degree. Can be made. Thereby, it is possible to prevent the occurrence of an impact on the wheel loader with the opening operation of the on-off valve 5.

本発明に係る作業車両用液圧制御装置の第１実施形態が適用される作業車両の一例として挙げたホイールローダを示す外観図である。BRIEF DESCRIPTION OF THE DRAWINGS It is an external view which shows the wheel loader mentioned as an example of the work vehicle with which 1st Embodiment of the hydraulic control apparatus for work vehicles which concerns on this invention is applied. 本発明に係る作業車両用液圧制御装置の第１実施形態を示す回路図である。1 is a circuit diagram showing a first embodiment of a hydraulic control apparatus for a work vehicle according to the present invention. 本発明の第１実施形態で得られる開閉弁の開口特性の一例を示す図である。It is a figure which shows an example of the opening characteristic of the on-off valve obtained by 1st Embodiment of this invention. 本発明の第１実施形態の負荷圧力とコントローラで設定される係数関数の関係の一例を示す図である。It is a figure which shows an example of the relationship between the load pressure of 1st Embodiment of this invention, and the coefficient function set with a controller. 本発明の第１実施形態の車速とコントローラで設定される係数関数の関係の一例を示す図である。It is a figure which shows an example of the relationship between the vehicle speed of 1st Embodiment of this invention, and the coefficient function set with a controller. 本発明の第１実施形態のオペレータの指示量とコントローラで設定される制御電流の関係の一例を示す図である。It is a figure which shows an example of the relationship between the instruction | indication amount of the operator of 1st Embodiment of this invention, and the control current set with a controller. 本発明の第１実施形態のコントローラが実行する処理の一例を示すフローチャートである。It is a flowchart which shows an example of the process which the controller of 1st Embodiment of this invention performs. 本発明に係る作業車両用液圧制御装置の第２実施形態を示す回路図である。It is a circuit diagram which shows 2nd Embodiment of the hydraulic control apparatus for work vehicles which concerns on this invention. 従来の作業車両用液圧制御装置を示す回路図である。It is a circuit diagram which shows the conventional hydraulic control apparatus for work vehicles.

符号の説明Explanation of symbols

３ ブームシリンダ
３ａ ボトム側圧力室
５ 開閉弁
A 閉位置
B 開位置
７ アキュムレータ
９ 分岐管路
１０ 分岐管路
１２ 電磁比例弁
１８ 圧力センサ（負荷圧力検知手段）
１９ 速度センサ（車速検知手段）
２０ 指示スイッチ（開度指示手段）
２１ コントローラ（制御手段）
２５ 絞り
２６ バイパス管路
２７ 切換弁
２９ チェック弁 3 Boom cylinder 3a Bottom pressure chamber 5 Open / close valve
A Closed position
B Open position 7 Accumulator 9 Branch pipe 10 Branch pipe 12 Proportional solenoid valve 18 Pressure sensor (load pressure detection means)
19 Speed sensor (vehicle speed detection means)
20 Instruction switch (opening instruction means)
21 Controller (control means)
25 Restriction 26 Bypass line 27 Switching valve 29 Check valve

Claims (7)

作業車両に備えられ、液圧シリンダと、この液圧シリンダの圧力室の圧力を制御する操作弁と、前記液圧シリンダの圧力室に接続管路を介して接続されたアキュムレータと、パイロット室を有し、且つ前記パイロット室の圧力に応じて前記接続管路の連通および遮断を切り換える開閉弁と、前記パイロット室への圧力の供給および排出を切り換える切換手段とを有する作業車両用液圧制御装置において、
前記切換手段は、前記開閉弁の開度を可変に制御する制御手段を含むことを特徴とする作業車両用液圧制御装置。 A hydraulic cylinder, an operation valve for controlling the pressure of the pressure chamber of the hydraulic cylinder, an accumulator connected to the pressure chamber of the hydraulic cylinder via a connection line, and a pilot chamber are provided in the work vehicle. And a hydraulic control apparatus for a work vehicle, comprising: an on-off valve that switches between connection and disconnection of the connection pipe in accordance with the pressure in the pilot chamber; and a switching means that switches between supply and discharge of pressure to the pilot chamber. In
The hydraulic pressure control device for a work vehicle, wherein the switching means includes control means for variably controlling the opening degree of the on-off valve. 前記切換手段は、前記開閉弁を制御する電磁比例弁を含むことを特徴とする請求項１に記載の作業車両用液圧制御装置。   The hydraulic pressure control device for a work vehicle according to claim 1, wherein the switching means includes an electromagnetic proportional valve that controls the on-off valve. 前記液圧シリンダの負荷圧力を検知し、その負荷圧力に応じた信号を出力する負荷圧力検知手段を備え、前記制御手段は、この負荷圧力検知手段から出力される信号に応じて前記開閉弁の開度を可変にさせることを特徴とする請求項１に記載の作業車両用液圧制御装置。   Load pressure detecting means for detecting the load pressure of the hydraulic cylinder and outputting a signal corresponding to the load pressure is provided, and the control means is configured to detect the on / off valve according to a signal output from the load pressure detecting means. The hydraulic pressure control device for a work vehicle according to claim 1, wherein the opening degree is variable. 前記作業車両の車速を検知し、その車速に応じた信号を出力する車速検知手段を備え、前記制御手段は、この車速検知手段から出力される信号に応じて前記開閉弁の開度を可変にさせることを特徴とする請求項１に記載の作業車両用液圧制御装置。   Vehicle speed detecting means for detecting the vehicle speed of the work vehicle and outputting a signal corresponding to the vehicle speed is provided, and the control means makes the opening degree of the on-off valve variable according to the signal output from the vehicle speed detecting means. The hydraulic control device for a work vehicle according to claim 1, wherein: オペレータの入力に応答して前記開閉弁の開度を指示する信号を出力する開度指示手段を備え、前記制御手段は、この開度指示手段から出力される信号に応じて前記開閉弁の開度を可変にさせることを特徴とする請求項１に記載の作業車両用液圧制御装置。   Opening instruction means for outputting a signal for instructing the opening degree of the on-off valve in response to an operator input, and the control means opens the on-off valve in response to a signal output from the opening instruction means. The hydraulic pressure control device for a work vehicle according to claim 1, wherein the degree is variable. 前記接続管路から分岐し、前記開閉弁に並列に配置されるバイパス管路上に設けられ、通常は前記バイパス管路を連通させ、前記液圧シリンダの負荷圧力が所定圧力以上になったときに前記バイパス管路を遮断する切換弁を備えたことを特徴とする請求項１に記載の作業車両用液圧制御装置。   When the load pressure of the hydraulic cylinder becomes equal to or higher than a predetermined pressure provided on a bypass line that branches off from the connection line and is arranged in parallel with the on-off valve. The hydraulic control device for a work vehicle according to claim 1, further comprising a switching valve that shuts off the bypass pipeline. 前記バイパス管路に、前記液圧シリンダから前記アキュムレータへの圧力のみを伝えるチェック弁を設けたことを特徴とする請求項６に記載の作業車両用液圧制御装置。   The hydraulic control apparatus for a work vehicle according to claim 6, wherein a check valve that transmits only pressure from the hydraulic cylinder to the accumulator is provided in the bypass line.
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